The present invention relates to deep wells which are drilled into the ground for extraction of fluid or gaseous materials. The invention particularly relates to oil, gas or hydrocarbon wells. Most particularly, the invention relates to means for providing instrumentation in the depths of an oil, gas or production well.
In drilling an oil well, it is customary to commence with a wellhead which provides a steel surface casing, generally around 46 cm (18 plus inches) in diameter. As drilling proceeds, successive sections of a steel intermediate casing are inserted, stage by stage, into the well bore, set in place with concrete slurry, and residual, set, internal concrete slurry plugs drilled out to continue the well bore down until a production zone, where hydrocarbon is found to be present in extractable quantities, is reached. Once contact has been made with the production zone, production tubing, of smaller diameter than the intermediate casing, is introduced down to the production zone, ready to extract hydrocarbon. A perforated production liner, intermediate in diameter (around 18 cm, otherwise 7xe2x80x3 or smaller)between that of the production tubing and that of the intermediate casing, may be extended beyond the end of the intermediate casing and the production tubing, allowing ingress of hydrocarbon into the production liner. The production liner allows hydrocarbon to flow into the production tubing but the intermediate casing is plugged, or sealed using a packer, against ingress of hydrocarbon from the production liner.
Fibre optic sensor line has been used, for some years, in the oil industry, to collect data from oil wells. The data collected primarily relates to temperature. Techniques exist whereby transmitted and backscattered light in a fibre optic line can be analysed to extract much useful information. Such techniques are not part of this invention. The instant invention is concerned, rather, with the introduction of a fibre optic line into an oil well.
Well data is of great economic importance, allowing the operator to give more effective surveillance to the well and thereby to enhance the productivity of the well. In these days of slimmer margins of economic viability in oil wells, and falling reserves, such data may be vital for the economy of the oil industry and, by extension, to the greater economy of the world, as a whole.
The fibre optic line is extremely fragile. It has a diameter, even with coating and sleeving, of no more than one millimeter. Its internal reflective properties can be compromised by surface contaminants. Being made of glass, it can shatter and break. It has a minimum radius of curvature below which it certainly breaks.
The environment in an oil well is extremely hostile. Drill bits, capable of penetrating hard rock, are lowered into the well and rotated with great torque by heavy steel tubes. Heavy steel casings are lowered into the drill shaft to line the shaft. The drill shaft is filled with cement and mud slurries. Residual cement plugs, once a slurry has set, are drilled out. An oil well represents a very hazardous environment for a fibre optic line.
In order to protect the fibre optic line from mechanical damage or contamination, it is customary to use control line. Control line, in the oil industry, is remarkably like metal hydraulic tubing, as used in industrial, agricultural and building site machinery. It is tough, usually 0.6 cm (xc2xc inch) in outside diameter, able to sustain high pressures up to 15000 psi (100 Mega Pascals), thermally conductive, can be joined in lengths by couplings, and provides a protected, clear channel down which a fibre optic line or electrical cable can be fed.
Installing a continuous length of fibre optic line, in the current art, requires the use of a continuous length of control line. Currently, to investigate an oil well, lengths of control line are strapped to the outside of a string of steel casings which are passes down the well to reach and to cross the zone of interest, where measurements are required or desirable. Alternatively, the control line is run inside a protective oilfield tubing string, on the inside of the well bore, down to and across the zone of interest.
Should the zone of interest turn out to be the required producing interval, it is customary to complete an oilwell by topping off the zone of interest with a set concrete casing and inserting a perforated production liner into and through the zone of interest. This creates a well with two separated strings of pipes, albeit concentric.
The completion of a well with a set concrete casing and a production liner precludes running a single length of fibre optic line, inside control line, down to and across the zone of interest, while maintaining the fibre optic line external to the well bore. The plug, through which the production liner passes, blocks off the end of the intermediate casing run, preventing the fibre optic line from passing out of the end of the intermediate casing and isolating the inside of the intermediate casing from the zone of interest.
When stimulating a well, a substantial advantage is gained by being able to gather distributed temperature data, without interfering with the near well bore area and without data being masked by the presence of a hydraulically isolated zone. When fibre optic line is installed on the inside of the well bore, the well bore becomes inaccessible to other tools. The control line and the (optional) protective tubing string reduce the room available for the tools. The fragility, even of a protective tubing string and control line protected fibre optic line, and the loss of room, mean that ancillary tools cannot be inserted or operated down a well bore where a fibre optic installation is maintained. Before ancillary tools are run down the well bore, it is necessary first to retrieve the fibre optic line. Stimulation of the well can then take place, or tools run, but without the gathering of data that could have a significant impact on well productivity.
With the fibre optic line in the well bore, any fluid flowing in the well bore can affect the fibre optic line. Its temperature readings no longer reflect, with accuracy, the temperature of the rock external to the well bore, but are altered or dominated by the fluid in the well bore.
An internally installed and maintained fibre optic line, in a string of protective tubing (pipes), restricts the flow of the well and requires a larger diameter well bore to accommodate the string of protective tubing/pipes and allow adequate flow. Well bores cost a great deal of money to create, and the price rises steeply with their diameter.
It is costly to install a control line across the producing interval. Therefore, a small diameter tubing, known as a xe2x80x9cstingerxe2x80x9d, is used to support the control line and lower it down the well bore into the region of interest or production zone. The present invention, as well as its other advantages, also seeks to provide means which eliminate the cost, time, and well incapacity that results from the intrusive use of a xe2x80x9cstingerxe2x80x9d.
The present invention has, as its object, the provision of apparatus, method and means, capable of allowing the introduction and maintenance of a fibre optic line, passing into and across the zone of interest, with a portion thereof external to the wellhead, capable of being maintained in position while other operations are carried out in the well bore, unaffected by fluids flowing in the well bore and eliminating the need for a well bore of increased diameter.
According to a first aspect, the present invention consists in an apparatus for providing a down-hole conduit for carrying an instrumentation line for use with a well bore in a substrate, the instrumentation line passing from the surface, towards the bottom of the well bore; said apparatus comprising: a hollow primary member, for insertion to extend into the well bore; said primary member comprising a first line of conduit on the outer surface thereof and primary coupling means for accepting the distal end of said first line of conduit; said apparatus further comprising a secondary member comprising a terminal conduit and secondary coupling means for accepting the free end of said terminal conduit; said secondary member being insertable through said hollow first member for said primary coupling means to couple with said secondary coupling means for the distal end of said first line of conduit to be coupled to said free end of said terminal conduit.
According to a second aspect, the present invention consists in method for providing a down-hole conduit for carrying an instrumentation line for use with a well bore in a substrate, the instrumentation line passing from the surface, towards the bottom of the well bore; said method including the steps of: inserting a hollow primary member to extend into the well bore; providing a first line of conduit on the outer surface of said primary member; providing primary coupling means for accepting the distal end of said first line of conduit; providing a secondary member comprising a terminal conduit and secondary coupling means for accepting the free end of said terminal conduit; and inserting said secondary member through said hollow first member for said primary coupling means to couple with said secondary coupling means for the distal end of said first line of conduit to be coupled to said free end of said terminal conduit.
The invention further provides for a method and apparatus wherein the primary member comprises a second line of conduit on the outside thereof; wherein the primary coupling means is operative to accept the distal end of the second line of conduit; wherein the terminal conduit is a loop of conduit; wherein the secondary coupling means accepts both free ends of the loop of conduit; and wherein the primary coupling means, on coupling with the secondary coupling means, couples the distal ends of the first and said second lines of conduit each to a respective one of the free ends of the loop of conduit; whereby the instrumentation line is passable through the loop of conduit back towards the surface.
The invention provides that the secondary member can be hollow and that the conduit loop is on the outside of the secondary member.
The invention further provides that the primary member and the secondary member, when coupled together, can form a continuous tube.
The invention further provides that the secondary member can be self locating on the primary member.
The invention further provides that the primary member can comprise a locating scoop, that the secondary member can comprise a locating tongue, and that the locating scoop and the locating tongue are co-operative to bring the primary coupling means and the secondary coupling means into angular registration for coupling as the secondary member is lowered through the primary member.
The invention further provides that the primary coupling means comprises one or the other of a coupling probe or a coupling socket and that the secondary coupling means comprises the other or one of the coupling probe or the coupling socket, and that the coupling probe and the coupling socket, on coupling, can form a sealed coupling between the distal end of one of the lines of conduit and one of the free ends of the loop of conduit.
The invention further provides a hollow modified member, the modified member having a secondary coupling means at its top end for accepting the proximal ends of two extension conduits, and having primary coupling means at its bottom end for accepting the distal ends of the two extension conduits, and provides that the modified member can be inserted through the primary member for the secondary coupling means on the modified member to couple with the primary coupling means on the primary member.
The invention further provides that a further modified member can be inserted through the modified member for the secondary coupling means on the further modified member to couple with the primary coupling means on the further modified member.
The invention further provides that the secondary member can be inserted through the modified member for the secondary coupling means on the secondary member to couple with the primary coupling means on the modified member.
The invention further provides that the secondary member can be inserted through the further modified member for the secondary coupling means on the secondary member to couple with the primary coupling means on the further modified member.
The invention further provides that the conduit can be control line and that the apparatus can be designed for use where the instrumentation line is a fibre optic line.
In the preferred embodiment, it is preferred that the primary member is set into the well bore with concrete or cement. It is further preferred that the well bore is part of an oilwell.
The invention is further explained by the example given in the following description and drawings